Natural fiber reinforced polymer composites have recently been investigated as a component of multilayered armor system (MAS). These composites were found to present advantages when replacing conventional high strength synthetic aramid fabric laminate composite (KevlarTM, with same thickness, as MAS second layer. Continuous and loose natural fibers were up to now mostly used to reinforce these ballistic composites. Only two natural fabrics reinforced polymer composite were so far used with same purpose. Therefore, this work investigated the possibility of substituting KevlarTM for three other natural fabrics, based on mallow and jute fibers, as reinforcement of epoxy composites. Fabrics made of either pure mallow, or 70%mallow/30% jute or 50%mallow/50% jute fibers were separately mixed with epoxy to produce laminate composite plates. These plates were set as second layer of Al2O3/Nb2O5 front ceramic MAS, that were ballistic tested against relatively high energy 7.62 mm ammunition. Indentation depth values caused by the bullet penetration in clay witness, simulating human body behind the MAS, were always found to be below the safety standard limit. These indentation values were similar to those obtained in MAS with KevlarTM as second layer. However, significant economical advantages favor the investigated natural fabric composites over the synthetic Kevlar.

Techniques for shock consolidation of powders have been developed for different purposes, including the synthesis of diamond from carbon powder. In this work, a new device configuration for dynamic consolidation is proposed. It consists of three coaxial tubes, with a conical cover made of explosive at the top of the device. The inner tube contains the powder to be compacted. The second is accelerated towards the first in order to promote its collapse. The third confines the explosive. A conical cap at the top of the device triggers the explosive. For a preliminary evaluation, two types of explosives, TNT and Composition B, were used. Preliminary analytical results by the impedance matching method indicate that maximum pressures of 35.44 GPa and 48.16 GPa could be achieved using TNT and Composition B, respectively. Maximum temperatures around 1,600 K and 2,500 K for TNT and Composition B, respectively, are expected. These pressure and temperature values are adequate for transforming graphite into diamond. Preliminary Rietveld refinement indicated that nanodiamond is a fraction of approximately 54% of the detonation resulting powder.

The ballistic performance of a multilayered armor with a front ceramic tile backed by a plate of giant bamboo fiber reinforced epoxy composite was assessed. The ceramic layer spalls the projectile, while the bamboo composite dissipates the remaining energy. Ballistic tests were performed with high velocity ammunition and the projectile penetration was evaluated by the intrusion depth in a clay witness. The average depth value of near 18 mm was found well below the limit specified by the NIJ standard of 44 mm and better than that for aramid fabric composite, about 22 mm, with the same thickness of the giant bamboo composite. The giant bamboo composite acts as an efficient barrier for the fragments originated from the ceramic brittle rupture. For practical application in portable armor for personal protection, the layer of giant bamboo composite presents not only a superior ballistic performance but also lightness and economical advantages over the conventional aramid fabric.

Multilayered armors with a front ceramic followed by aramid fabric (Kevlar™) are currently used against high velocity ammunition. In these armors, a front ceramic layer that shatters and spalls the bullet is followed by an intermediate layer, usually plies of aramid fabric, which dissipates both the bullet and ceramic fragments energy. In the present work, the intermediate aramid fabric layer was replaced by an equal thickness layer of 30 vol% jute fabric reinforced epoxy composite. Ballistic impact test with 7.62 caliber ammunition revealed that both the plain epoxy and the jute fabric composite have a relatively similar performance of the Kevlar™ and also attended the NIJ standard for body protection. The energy dissipation mechanisms of jute fabric composite were analyzed by scanning electron microscopy and found to be the rupture of the brittle epoxy matrix as well as the interaction of the jute fibers with the post-impact fragments. This latter is the same mechanism recently disclosed for aramid fabric. However, the lightness and lower cost of the jute fabric composite are additional advantages that favor its substitution for the aramid fabric.